DE3103852A1 - POWER AMPLIFIER - Google Patents

Description

PATENTANWÄLTE FW. HEMMERICH GERD MÜLLER D. GLOSSE F. POLLV-FIER

73 * 7 U - bh -

Tokyo Shibaura Denki Kabushiki Kaisha, 72 Horikawacho ₉ Saiwai-ku, Kawasaki-shi, Kanagawa-ken (Japan)

Power amplification r

This invention is concerned with a power amplifier, however, it is concerned in particular with such a power amplifier, which has a noise suppression circuit or has to have a tuning circuit, which then takes effect and works when an exceptionally strong signal is switched on.

One of those with the design and construction of transistor-populated Problems associated with power amplifiers is that they are instantly turned on and commissioning of the power amplifier a surge current with an extremely large amplitude flows through the power transistors, with as a result of which a noise or other undesirable phenomena can occur in the consumer, sometimes even the power transistors and the consumer can be destroyed.

The use of voting circuits / noise blocking circuits, with which the occurrence of noises and undesirable phenomena part as well as the destruction the power transistors and the consumer are to be prevented, is in the field of power amplifier construction well known. A weakening or a noise barrier is achieved by that in the current path of an amplifying transistor arranged in front of the power transistor electronic switch is used. In the previously known constructions and performances switches the electronic switch the amplification

13Ü067 / 052S

PATENTANWÄLTE FW HEMMERICH - GEFiD MÜLLEN · D. GHOSGc · F. POLL '/' FIER ⁷ ^

- bn -

However, the sistor does not turn off completely, so that when a strong signal is applied, -on Part of the input signal is passed through the amplification transistor to the power transistor and - not quite as strong as it is without an electronic control switch - noises and causes other phenomena to arise.

The invention thus has the following tasks:

To create a power amplifier that one Have tuning circuit or noise blocking circuit has what exceptionally strong signals suppressed and thereby effectively and completely prevents overloading of the power amplifier.

To create a power amplifier that has a tuning circuit or noise blocking circuit which has an exceptionally strong input signal after switching on and I ηbe of the amplifier is suppressed for a given period.

To create a power amplifier that one To have tuning circuit or noise blocking circuit has which undesirable changes in the pending at the output terminal of the amplifier Can suppress potential during the Abs t iminzus tandes or attenuation state.

The invention solves the problems set for it in that it provides a power amplifier,

130067/0525

PATEN FAMWALTE F W. HEMMERICH · GEFD MULLE * · D. GHOSSR · F.

7 3 4 - bh 2 6.1.1981

310 3 8

from the circuit components listed below composed of: - a preamplifier stage with at least one transistor, this one Transistor with first, second and third terminals, of which the first transistor terminal is connected to a single circuit, of which the second connection of the aforementioned at least one transistor to the input of a Lei s turujs amplifier stage connected is; from an electronic switching device, which in terms of circuitry between the third terminal of the aforementioned at least one transistor and a second power supply terminal is arranged and has a Steuerurigsan sch Iu [J; from a resistance system, which circuit-wise between the third Connection of the aforementioned at least one transistor and the first power supply connection is arranged, and this in parallel to the already mentioned at least one transistor and the control circuit, which is connected to the control terminal of the electronic switching device and such is constructed and designed so that a change in the signal level leading to an overload condition is measured and detected and that in response to this signal level the electronic Switch a tuning signal or attenuation signal is switched on.

In the preferred embodiment, include to the power amplifier: - a power amplifier stage; one for the dowry and driving the

130067/0525

BATH ORIGINAL

PATENTAfJVvALIf "F V'J Hf-MMl PMJH · GH-L MIM ί [-Ί · [J GPf ir.F - f FO! M ^r 'IPF-. / ^.: 4'O

- bl. - ψ 7A-. 1.1981

31 0 3 B b

Efficiency loss fat kers iuf e certain advance delivery level with a transistor whose base is connected to the input circuit, its collector both led to the power gain study is as well as a loading device on the first power source connection and its emitter with a second power source connection in connection stands; an electronic switching device that selectively either with the emitter of the transistor belonging to the preamplification stage to the one power source terminal or to the second power source terminal in response to a tuning signal or weakening signal connects.

The subject of the invention is thus a power amplifier of a tuning circuit or noise barrier circuit, which then switches the power transistor into an attenuated state when it receives an exceptionally strong signal. The power amplifier includes: a preamplifier stage (10) and a power amplifier stage (12). The preamplification stage (10) has at least one transistor (Q _a ) for controlling and driving the power amplifier stage (12). The emitter of this transistor is led via an electronic switch (26) on the one hand to the second current source connection and on the other hand via a resistor (32) to the second current source connection. When a pending overload is detected, the electronic switch is opened via the emitter of the transistor and disconnected from the second power source connection terminal.

130O67 / OS25

PATENTANWÄLTE f .V »'. HFiMML RIUH · GERD MULLE * ■ O. Gf'OS'-F · Γ. FOLLMüKR 7? 4th

<f £ 6.1.1981

- -ir -

31 0 3 3 b

The invention will now be based on the embodiment shown in the drawing (the Embodiments shown in the drawing) in more detail explained. The drawing shows in: -

Fig. 1 The one used with a power amplifier Tuning circuit or noise blocking circuit of this invention,

Fig. 2 is a circuit diagram of another power amplifier with a tuning circuit or Noise barrier scarf tuny this Ertindugn.

Fig. 3. The circuit diagram of yet another embodiment of the power amplifier with a Abs I i (switchover or noises Ii block switch of this invention.

Fig. 4 The circuit diagram of a compared to FIG. 3 changed and modified mood control circuit or noise control regulation 1 circuit.

Fig. 1 shows a power amplifier incorporating a tuning or noise cutoff circuit of this invention. This power amplifier includes: - a pre-amplification stage lü; a power amplifier stage (12) and a consumer, for example a 1 aiii ^r -pt edier 14. The preamplifier stage (10) is assigned a transistor Q and this transistor \\ is with its base terminal via a coupling capacitor C, to the input terminal 16 of the preamplifier stage (10) led. The collector of the Transitüfi Q. is at one end of a collector

el

1 astungsverbindungen 18 connected, the other

130087/0525

BATH

PATENTANWÄLTE FW HEMMERICH · GERD MÜLLE * · D. GKuS: - "=. ■ F. K) LLl> /. Tl ^fc Fl 73 4

- b) \ - 3 26. i. 1981

End again via a connection 24 and via the power switch 22 to the current source / voltage source 20 is connected. The emitter of transistor Q is via electronic switch 26, which follows will be described in great detail, led to the ground potential 22.

The input connection 28 of the power amplifier stage 12 is to take over the preamplification signal via a coupling capacitor C _? connected to the collector of the transistor C) belonging to the preamplifier stage 10. The output signal of the

Power amplifier stage 12 is transmitted to loudspeaker 24 via output terminal 30.

The switching transistor Q belongs to the electronic switch 26. The collector of this switching transistor Q is with the emitter of transistor Q vers a

bound, whereas the emitter of this switching transistor is connected to the ground potential E. The collector belonging to the switching transistor Q is furthermore also via a resistor 32 to the current source connection / voltage source connection 24 led. At the input terminal 32 of the electronic Switch 26 is the base terminal of transistor Q, and with this input terminal 32, a control circuit 34 is connected in such a way that the base of the transistor Q is a control signal can be switched on.

The function and mode of operation of the circuit shown in FIG. 1 will now be described below will : -

130067/0525

PATENT ADVOCATE F.W. HEMMERICH GERD MULLES D. & Π05Γ, Ε F. POLLVEIEH ''>

/ lo l ⁶ - \

After closing the fletzscha i ters 22 is immediately a pulse signal at the input connection 16 of the pre-amplification stage IO, and this signal the base of the transistor () is switched to. The regulator circuit 34 connected to the power supply unit 20 is locked, transmits to the electronic switch 26 a control signal or regulation signal. This control or regulation signal up for the lapse of a predetermined time equal to zero, so that as a result of this, the switching transistor Q <ini LOCKED STATE or SHUTDOWN STATE is held. During this time there will be a resistance 32, which is connected to the power supply part or power supply 20, the emitter of the transistor L)

and the collector of transistor Q is held at the same potential. That in turn means that dabi
is

while the transistor Q is completely switched off

Thus, the entire power amplifier is during the one on the closing of the Metz counter 22 the following predetermined time is kept in a state of decline or weakening, that undesirable phenomena, for example the noise of the loudspeaker 14 or the damage to the power transistors in the amplifier output stage 12 can be prevented.

After the specified time T has elapsed, this changes from the Reg lerscha 1 active 34 on the basis of the Transistor Q transmitted control signal or

OR | _QiNAL

130067/0525

EV-TFf-jTAf-JWAUE Γ-.W HtMWFRiCH - αν VS) IJ ¹ IH 1 S 'Λ ■ D GPGi ¹ P f {f -. ( _L f-'M. L ·. <I 4'0

31038B2

The control signal has its signal level in such a way that with this signal the switch ttransi; -1 or Q is brought into the on state or ON STATUS when the power supply current has leveled itself to the normal operating state. The transistor becomes permeable and puts the collector to earth potential, which in turn means that the transistor () is now also in the through! ai'-zu found is switched, the input signal is amplified and this amplified input signal is then passed on to the power amplifier stage 12. This is the point in time at which the transistor Q is connected _{to Lrde or Marse by being controlled via the switch transistor Q c} and is in fact disconnected from the power supply unit. If stage 12 is working under normal conditions, you amplify these on switched input signals and then forward them to loudspeaker 14.

Now the power start can also be protected from overload. For this purpose, the regulator circuit 34 is connected to an upper t τ feinm ^ ßschal tang - (this circuit is not shown); which belongs to the power amplifier tute 12 . During normal operation, the controller chal tunu 34 from the basis of the switching transistor ?. Q. aufqescha] let a control signal or regulation signal that keeps this switching transistor Q in the Out chi auzus tami.

FliefSt because of an exceptionally strong fingany "signal or because of a short-circuit, too strong a current through the power transistors and through the loudspeaker for 14 _seconds then the regulator

130067/05

ΓΑΤΕ NTANW / LT [■ Γ .VV. HtMMElHICH · GfRD MULLM · D. GIiOSi H

• F. KT.ifAtlSR / - '4

- bh 01/26/1981

circuit 34 removes the control signal from the base of the switching transistor Q and brings this switching transistor Q _s thereby in the SWITCH-OFF STATE or SPCRFiZUSTANt), which in turn causes the emitter of the transistor () no longer to ground or

Ground is connected to the power supply part or power supply unit 20 again via the resistor 32 is. The transistor Q is completely

dig is switched to the blocking state and then prevents the signal from entering the power amplifier stage happened. If the condition of the connection of an excessively strong current has been reversed is - and the elimination of the overload state is measured by the overcurrent measuring circuit and then the base of the switching transistor Q is detected by the regulator circuit 34, the is locked with the overcurrent measuring circuit, again the control signal or regulation signal switched on and the switching transistor Q thereby back to SWITCH-ON or DURCHLASSZU-STAHl) brought. This in turn also brings the transistor Q. into the ON STATE or THROUGH-LASSZUSTAIH), which in turn has the consequence that the input signal amplifies the signals and the amplified signals then the power amplifier stage 12 switched to will.

The circuit diagram of a is shown with E ig «2 direct-coupled and quasi-complementary push-pull lei stungs insurer of this invention.

BATH ORIGINAL

1300G7 / 0B25

PATENTANWÄLTE FW HEMMERICH · GERD MÜLLER · D. GROSSE · F. K) LUlEiER / ~ i '] / Q

- bra -

3103052

A preamplifier stage 10 consists of a first differential amplifier 40, a second differential amplifier 42 and a driver amplifier / control amplifier 44. The first differential amplifier 40 includes the two field effect transistors (FET) Q. τ and Quo 'we 1 before a resistor 46 are connected to one another, which in turn is connected to earth or ground via a center tap and a resistor 48. The control gate of the field effect transistor (FET) Q,, is connected to the input terminal 16, whereas the control gate of the field effect transistor (FET) Q, ^ is connected to the output terminal 30 of the power amplifier stage 12 via a feedback circuit 34. The collector connections of the field effect transistors (FET) Q 1 and (FET) Q 1 are each led to the power supply or the Hetzteil 20 via the resistors 50 and 52.

The two MPN transistors Q, and Q,? »Belong to the second differential amplifier 42. the emitters of which are connected to one another and also via a common emitter resistor 56 and via the electronic switch 26 - this electronic switch is designed corresponding to the electronic switch 26 shown in FIG. 1 - are connected to ground or earth. The collector connections of the transistors Q ₃ -, and

Q ₀ are in each case above the applicable a c

Collector resistors 181 and 182 on the power supply or led to the power supply unit 20. the

30067/0526

PATENTAMWALfE F.W. HEMMERICH GERD MÜLLER - D. GROCSE - F. POLLMEIF.P? /O

- bra -

January 26, 1981

Transistors Q ₁ and Q 2 have their base connections to the collector connections of the field effect transistors (FET) Q ₁ , 1 and (FET) Q 2.

The driver amplifier / control amplifier 44 has a PNP transistor Q, the emitter of which is led to the power supply or the power supply 20 is, whereas the transistor Q via its KoIlektoranschluss via that from the driver circuit 58 and the collector load resistor 60 existing series connection is connected to earth or earth E. With its base connection is the transistor Q connected to the collector connection of the transistor Q o.

The output stage or power amplification stage 12 consists of the two mutually complementary transistors Q ,, and Q, "and the two NPN power transistors Q - | and Q _e2 - via the base terminal of the NPN transistor Q, -, is connected to the collector terminal of the driver transistor Qc ¹ , while the base terminal of the PNP transistor Q.ρ _{is connected to the collector terminal of the transistor Q-2 via the driver circuit 58} is. The emitters of the transistors Q, ₂ are connected to the output terminal 30 via the Eiii tterwideristors 62 and 62, respectively. The collector connection of the NPN transistor Q 1 is connected to the power supply or to the power supply unit 20, whereas the collector connection of the PNP transistor Q _{12 is} connected to earth or earth E.

BATH ORIGINAL

■ - ■ AT LUt Af JWALTf ". F Λ \. HLMMf-RICH · CH Ri) MtJLI FR D CiHO: 5 Γ · F." OLl Mf Ii S /. * · '

- till - . ^ 2 6.1.1981

fS - J * -

üie Basisansch 1 lisse (Jer NfMl power transistors Qi and Q ₁ - are each led to cjie emitter connections of the complementary transistors Q, -, and Q, _? . At its collector is the power transistor Q ι with the power supply or the power supply 20 in compound and mild its emitter connected via an emitter resistor 66 output severally! ow 30. the KOI lector terminal of the power transistor Q ₁ O is connected to the output terminal 30, i while the emitter of this transistor via an emitter resistor 68 to earth or ground e Ge puts st.

The electronic switch 26 includes an Nf ¹ N switching transistor Q _c , the collector terminal of which is connected via a common emitter resistor to both the emitter terminal of the transistor Q-] and to the emitter terminal of the transistor Q ₀ and also to the other is passed via a resistor 32 to the power supply or the power supply unit 20. The emitter of the transistor Q is connected to earth or ground L.

A timing element circuit 70, which is composed of a parallel connection of a capacitor 72 and a resistor 74, belongs to the regulator circuit 34. The tndc of the timing circuit 70, marked with the general reference number 76, is connected to the power supply or the power supply 20 via the resistor 78, while the other end of the timing circuit is connected to ground or E. But tuny 31 is part of the controller scarf

130067 / 0S25

^BATH

PATf.NTANWAl T [Γ AV HLMMrRICH · (if HD MUl IΪ R ■ l>. GRO-.SL f. ' ¹ Ol' Mf! LR 7 3 ί 7 ϋ

- I) Il ZG.1.1981

fib?

also another one as a Kopp! Utigsgl ir; d executed circuit 80 with an NPH transistor Q., which circuit-wise is arranged to see the connection of the timer circuit 70 marked with the general reference number 76 and the Lmi t ter connection of the conduction transistor Q ₁ ^. The transistor Q is connected to its collector connection and the resistor 79 is connected to the connection 7 G of the timing circuit 70 Ii with its emit. The connection is connected to the transistor \\. to earth or Hasse E, while the base terminal of this transistor Q _f via the diode!), and from the resistor 31 existing rectifier circuit to the KoIlektoran circuit of the power unit transistor Q "is performed. The connection of the Zn itgliedschaltuny marked with the general reference number 76 is connected to the circuit. the base connection of the switch ttransi storr. Q associated with the electronic switch 26.

The following is the function and mode of operation; the one with fig. : 'shown 11 tt-n circuit - and this Function and mode of operation is generally that described in connection with the circuit of FIG Function and mode of operation are explained in a similar way: -

Closing the power switch 2? causes that at the AnM.iiluh 76 the time element 1 unq 70 the ansteheixif [ ^: ot <-ntial from zero from we;: eü dci charge di- .:! (itu.ieiii itors Ί ?. becomes gradually stronger. IJas v / it'di ι i: .-- i hai tjy tol-je that the TriHisistor Q _c sii 1 a ϋ [U- \\ " !! if> rr ^/;! v iiid 'or Ahsrlial t to t at> d comparable?

130067 / 0B25

PATENTANWÄLTE FW HEMMERICH · GEiHtJ MÜLLER ■ D. GROHSE F. I ¹ ULi MEIER 7 3 4

- Ml - 2 6.1.1981

r> - J

remains and is held until the potential applied to terminal 76 of timing circuit 70 has reached a voltage which is strong enough to switch the holding transistor Q into the SWITCH-ON STATUS or PASSAGE STATUS.

This in turn causes the potential of the power supply or the power supply unit 20 via the resistors 32 and 56 to the emitter terminals of the transistors Q _η and Q ,, is switched to aeschal in such a way that

3 1 ac.

thereby the two transistors belonging to the second differential amplifier 42 (K ₁ and Q _{o in this way}

ai ac

are controlled and driven so that they switch to the SWITCH-OFF STATE or LOCKED STATE and then block the passage of the signals to output terminal 16. The power amplifier is thereby held in the attenuated state or tuned state, with the result that the occurrence of noise and other phenomena in the speaker 14 is prevented, but also damage and destruction of the loudspeaker 14 or the power transistors Q -j and Qpo

The rise of the potential at the base of the switching transistor Q to a sufficiently high voltage causes the transistor Q to switch to the ON STATE or CONDUCTED STATE and thereby the ground potential or ground potential leads to the collector of the switching transistor (J _s . This also brings the second differential amplifier 42 in normal working condition, whereby

1 -J 'J' - '

PAFEMrAMWALTE FW HEMMERICH · GEHD MÜLLER · U. GROiSE · F. POLlMHE '· -; · '? 1 7 (J.

- bn 26.1.19 a

the second different! al amplifier 42 then the front first differential amplifier 40 switched on Signal amplified and passed on to the driver amplifier or control amplifier 44. That has result in the power amplifier working normally, The common emitter potential of the second Differential amplifier 42 is from the power supply or the Metzteil 20 because the end of the resistor 30, to which the collector of the transistor Q is connected, to ground potential or ground potential lies.

If an overcurrent or excessive current caused by an input signal that is too strong or a short circuit flows through the power transistors Q - and Q 2 as well as through the loudspeaker 14, then the voltage across the resistor 68 will also be so great that the transistor Q _f switches to EIHSCHALTSTAND or TRANSLATION STATE and thereby causes the transistor Q to switch the Basispotenti ales to the ground potential or ground potential. The transistor Q goes into the LOCKED STATE or SWITCHED OFF STATE and controls the second differential amplifier 42 in such a way that this second differential amplifier 42 also switches to the LOCKED STATE or SWITCHED OFF STATE. As long as the overcurrent condition exists and is not reversed, the input signal can therefore no longer reach the power amplifier stage 12. üa-3 but means that the power amplifier works uikI works in such a way that damage and destruction of the Le is tun ^r js trans i interfere and de. L πι tfipr'icruirs is prevented by overflows.

^ß AD ORIGINAL

1 3 - "> 0?> 7 /

PATf NTA? U ";iff-" f W HEMMtHICH ■ GI FO MULI! l · P GHOlSE ■ Γ. - ³ Ol ■ M! ü h , '? 4/0

- Is η Γ: (.1,1901

31038 ^ 2

Subject of the nil Mq. Switching the displayed image 3 is -.! "Is a ausnangskondensatnr1 oser I (Ji-L) and direct-coupled power amplifier diener invention, namely an output capacitor-less, direkl coupled Lei stunyi reinforced är \ he purely complementary embodiment the riding complementary embodiment is substantially qleich the qua? · i L owp lenient a'ren construction and Aurrfuhruny by Ma.?. the ausganurkondensator lor.-o execution or (corresponds JUEL execution η with from the power supply circuit or incitement teeth i 1 scarf tuny, the output-coupled Kondetis atorkreis according to Fig. ?.

The operation of the iE.it Mg. 3 wiedergeyebenen complementary Lei ί · tu ngst ransi stortai Q-, and Q represents ₀ corresponds to that of the nit Fig. 2 yej.te 1 1 It ti power transistors U-, and Q r>. The other Scha 11. u η gsk omp ο η e η te η, ie de rerste Π iffere η t. ia I amplifier 40, üar / wide Dif f'erc-nt'i al \ ei stat Ler 42, the driver versfäri rr or Steue! Unqs amplifiers 44 "all of which belong to the pre-amplification unit 10, work and function in such a way" as has been described and described for the circuit components shown in Fig. 2.

The nii t Fig. 3 shown Le i ■ - tuuusvt; si arker is fed with the second di tf eren ti al yi; i:> t at t ers <17- voii a s ^ eizteil or a st ν n ^ vet · .oryunijs 1 · - i 1 ₃ vitlc hc-s / * ns chi ü: -Si "i for i> (« siti ve *. ['■: .. t ft-i i ^ ί and for neqati.es Γό tpn t "ia I I - ;;!, ine pf - iiiv N> / I> ■ i 1 s μ.ιη-t'ung -i-Vtc viird de: '; tri-tcr ^ sd'J-il · - .4 · ΐ «-'. Ul 1 / Λ ι i! ■ - ε Γ; 'j'.: r dor SI ϊ · ..-! - '= v "f- ϊ ι- · ί « ιιη_: · μ: Ι <. \ ι \> Ui} ι · _: \ , \, Nb ί Myegeu

BADORSGiNAL

ι 3ο ( ^; f.7 η) ¹ ./ ί-

PATENT LAWYERS F.W. HEMMERICH GERD MÜLLER D. GRGSSt F. POLlMKIER 73

-Dh-26.1.1981 ZO -

the negative power supply voltage -Vcc via the second connection 82 of the power supply part or power supply and via the resistors 46 and 48 the case arisch 1 üssen of the field effect transistors (FET) Q., and (FET) Q _,? is supplied and activated. The negative line voltage -VCC is also still supplied to the collector terminal of the driver transistor Q via the emitter resistor 60 and via the driver circuit 58. The negative power supply voltage will also continue to be applied to the collector connections of the NPN transistors Q _? and Q _? each switched on and fed.

The L ^: mid-connections of the transistors Q ·, and Q ₀

ai absind across the common emitter resistor 56 and Connected via deb to the electronic switch 26 belonging switching transistor Q to ground or E ground. As can now be seen from FIG. 3, the electronic switch 26 also includes an NPH transistor Q--, the circuitry between the driver circuit 58 and the Uetzti1an connections 82 arranged and together with the two diodes, which are between the Asian connector and the case connector this transistor are switched, takes over the function of a collector load circuit. With his The base connection is the transistor Q via the NPH transistors Q. and Q. led to the end 76 of the tuny 70 timer.

The power amplifier shown in FIG. 3 now works in such a way that the switching transistor is tor Q

130067/0525

PATENT LAWYERS F.W. HEMMERICH ■ GERD MÜLLER - D. GRGSSE · F. POLLMrIER 73 4 "/ C

- bra -

January 26, 1981

24 - w -

functions as it has been described in connection with FIG The result is that the negative terminal voltage, which is present at the second terminal 82, when the power amplifier is operated in the attenuated state or tuning state, then connected to the collector terminal of the transistor Q in such a way that the NPW transistors Q.-, and Q, thereby are controlled in such a way that they are brought into the ELFI SWITCHING STATE or DURCHLASSZUSTAfID. That leaves a situation. arise ₃ in v / elcher the transistors Q.λ ^un ^ ^ e2 ^unc * ^ ^ΘΓ loudspeaker 14 are exposed to the risk of damage or destruction, even if the amplifier is operated in the attenuated state or tuned state because the current is from the second connection terminal 82 from through the transistors Q, ₂ and Q "as well as through the loudspeaker to earth or to earth E flows.

The modulation and control of the transistor Q takes place together with that of the switching transistor Q according to FIG. 3 by the regulator circuit via its base connection to the timer circuit 70. Thus, the transistor Q, together with the switching transistor Q _s ann, goes into the SWITCH-OFF STATE or the BLOCKED STATE when the Mains switch 22 is closed or if an overcurrent or excessive current flows through the transistors Q 1 and Q ″, so that in turn destruction or damage to the transistor parts Q 1 and Q ″ and the loudspeaker 14 is prevented.

130067/0525

PATENT LAWYERS F.W. HEMMERICH · GEHD MÜLLER · D. GROSSE · F. POLLMCIER 73

- bra -

January 26, 1981

The circuit diagram of another regulator circuit shown in FIG. 4 is a regulator circuit that is changed and modified compared to FIG. The base terminal of the switching transistor Q belonging to the electronic switch 26 is fed to the timing circuit 70 via a Schmidt trigger 84. The output 86 of the Schmidt trigger 84 is connected to the transistor Q, which belongs to the driver circuit 44. The collector terminal of the transistor Q via a common emitter resistor 56 to the emitter terminals of the transistors Q, and Q is _Q

al ac.

Verbudnen, while the collector connection of the transistor Q is fed to the collector terminal of the driver transistor Q via a driver circuit 58 is. The Schmidt trigger 84 consists of the two cascaded NPN transistors Q. and Q, whose input terminals are connected to one another and are connected to earth or earth E via resistor 88

Transistor Q. to transistors Q and Q ge-K s g

leads, while the transistor Q. via its base terminal connected to the timer circuit 70 is.

The output level at output terminal 86 of the Schmidt trigger 84 then suddenly becomes stronger when that which is pending at the B-is connection of the transistor Q- Potential assumes a value that is greater than the threshold voltage of the Schmidt trigger is, and then drops again when the base potential below the switch-off level of the Schmidt trigger lietjt .. During operation, the loading

130087 / 052B

PATENT LAWYERS F.W. HEMMERICH · GERO MÜLLER · D. GROSSF- · F-. P (JL'.M - It R 7 3 4

- bh 01/26/1981

23 -

voltage of the timer circuit 70, (and this is the base potential of the transistor (} ■), the input

Switching level for the duration of a predetermined time after closing the power switch 22 or after removing an overcurrent condition, which in turn has the consequence that the output voltage at terminal 86 - and thus also the potential at the base terminal of the transistor Q suddenly increases and becomes so strong that the transistor Q _{5 is} immediately brought into the ON STATE or ON STATE. If, on the other hand, the charging voltage of the timing circuit 70 falls - or the potential applied to the base of the transistor Q. - then this has the consequence that the transistor Q immediately goes into the DISABLED STATE or the DISABLED STATE. This means, however, that the transistor Q can change and switch between the states of passing and blocking in a stable manner around the threshold value of transistor Q.

This invention can now also be modified in this way be modified so that the regulator circuit 34 only cooperates with the power amplifier unit 12. This change can be achieved in that the with Fig. 2, fig. 3 or 4 reproduced Circuits without capacitor 72 are operated. In this case they work with FIG. 2 or the wide stands 74 shown in FIG. 3 and 78 only as a Vovspanriunyskreis with one Time constant of zero for the switch belonging to the electronic switch 26 »ansistör U. ·

BATH ORIGINAL

130067/0025

Claims (1)

PATENT LAWYERS F.W. HEMMERICH GERD MÜLLER D. GROSSE F. POLLMEIER - 21 - February 4, 1981 gr.ni 73 470 Tokyo Shibaura Denki Kabushiki Kaisha, 72 Horikawacho _f Saiwai-ku, Kawasaki-shi, Kanagawa-ken (Japan) Patent claims: Power amplifier, characterized by a preamplifier stage (10) which has at least one A transistor having first, second and third terminals, the first terminal is connected to an input circuit, a power amplifier stage (10), the input of which is on the second terminal of the transistor is performed, an electronic switch (26) which between the third connection of the transistor and the second connection terminal of a power supply unit (20) is arranged and has a control connection, a resistor system (32) which is parallel to the transistor between its third terminal and the first connection terminal of the power supply unit (20) is arranged, and by a control circuit (34) connected to the control connection is connected and each signal level tending to become stronger is detected and then due to of the respectively detected signal level on an attenuation signal the electronic switch (26) switches on. 2. Power amplifier according to claim 1, characterized in that the control circuit (34) is the electronic switch (26) switches on a damping signal in order to achieve that the power supply unit (2O) from the power amplifier stage (12) for a specified time starting with the activation of the power supply unit (20)? is separated. - 22 - ■ 130067/0526 PATENT LAWYERS F.W. HEMMERICH · GERD MÖLLER · D. GROSGE · F. POLLiv.Eltfi "22 - 3. Power amplifier according to claim 2, characterized in that that the control circuit (34) includes a timing element (70) which is charged by the power supply unit (20), and that the damping signal remains switched on to the electronic switch (26) as long as that on the timer (70) the applied voltage is below a specified nominal value. 4. Power amplifier according to claim 3, characterized in that that the voltage present at the timing element (70) is switched directly to the electronic switch (26), when the magnitude of this voltage is smaller than a specified target value. 5. Power amplifier according to claim 3, characterized in that a Schmitt trigger (84) belongs to the control circuit (34), which is connected to the timer (70), and that the damping signal via the Schmitt trigger (84) the electronic switch (26) is switched on. 6. Power amplifier according to at least one of claims 1 to 5, characterized in that the control circuit (34) applies the damping signal to the electronic switch (26) switches on when in the Power amplifier stage (12) a current flows which is greater than a predetermined current strength. 7. Power amplifier according to claim 6, characterized in that that the control circuit (34) is assigned a bias circuit (58), the damping signal being the electronic Switch (26) is switched on when the voltage of the bias circuit (58) due to a predetermined Value of the exceeding current drops. 130067/0525 PATENT LAWYERS FW HEMMERICH · GERD MÜLLER ■ D. GROSSE · ?. POLbVlEIEfi ^{? J} 8. Power amplifier according to claim 7, characterized in that that the control circuit (34) includes a parallel circuit, which between the bias circuit (58) and the Power amplifier stage (12) is arranged to the To reduce the terminal voltage on the bias circuit (58) when there is a current in the power amplifier stage (12) flows, which is stronger than a predetermined nominal current strength. ο power amplifier according to at least one of claims 1 to 8, characterized in that the electronic switch (26) is is a transistor. 10. Power amplifier according to at least one of claims 1 to 9,
characterized in that the power amplifier stage (12) has two transistors with opposite conductivity, which serve to amplify the negative and positive half-waves of the input signal, that a driver transistor (Qc) is provided whose Collector connection is connected to the common base connections of the two transistors, that an active load transistor between the collector terminal of the driver transistor (Qc) and the first Terminal of the sharpening device (20) is arranged, and that the power amplifier has a second electronic Has switch, which between the base terminal of the active Beleistungstransistor and the collector circuit is arranged » 1 30087 / 082S